path: root/fs/xfs/scrub/iscan.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (c) 2021-2024 Oracle.  All Rights Reserved.
 * Author: Darrick J. Wong <djwong@kernel.org>
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_log_format.h"
#include "xfs_trans.h"
#include "xfs_inode.h"
#include "xfs_btree.h"
#include "xfs_ialloc.h"
#include "xfs_ialloc_btree.h"
#include "xfs_ag.h"
#include "xfs_error.h"
#include "xfs_bit.h"
#include "xfs_icache.h"
#include "scrub/scrub.h"
#include "scrub/iscan.h"
#include "scrub/common.h"
#include "scrub/trace.h"

/*
 * Live File Scan
 * ==============
 *
 * Live file scans walk every inode in a live filesystem.  This is more or
 * less like a regular iwalk, except that when we're advancing the scan cursor,
 * we must ensure that inodes cannot be added or deleted anywhere between the
 * old cursor value and the new cursor value.  If we're advancing the cursor
 * by one inode, the caller must hold that inode; if we're finding the next
 * inode to scan, we must grab the AGI and hold it until we've updated the
 * scan cursor.
 *
 * Callers are expected to use this code to scan all files in the filesystem to
 * construct a new metadata index of some kind.  The scan races against other
 * live updates, which means there must be a provision to update the new index
 * when updates are made to inodes that already been scanned.  The iscan lock
 * can be used in live update hook code to stop the scan and protect this data
 * structure.
 *
 * To keep the new index up to date with other metadata updates being made to
 * the live filesystem, it is assumed that the caller will add hooks as needed
 * to be notified when a metadata update occurs.  The inode scanner must tell
 * the hook code when an inode has been visited with xchk_iscan_mark_visit.
 * Hook functions can use xchk_iscan_want_live_update to decide if the
 * scanner's observations must be updated.
 */

/*
 * If the inobt record @rec covers @iscan->skip_ino, mark the inode free so
 * that the scan ignores that inode.
 */
STATIC void
xchk_iscan_mask_skipino(
	struct xchk_iscan	*iscan,
	struct xfs_perag	*pag,
	struct xfs_inobt_rec_incore	*rec,
	xfs_agino_t		lastrecino)
{
	struct xfs_scrub	*sc = iscan->sc;
	struct xfs_mount	*mp = sc->mp;
	xfs_agnumber_t		skip_agno = XFS_INO_TO_AGNO(mp, iscan->skip_ino);
	xfs_agnumber_t		skip_agino = XFS_INO_TO_AGINO(mp, iscan->skip_ino);

	if (pag->pag_agno != skip_agno)
		return;
	if (skip_agino < rec->ir_startino)
		return;
	if (skip_agino > lastrecino)
		return;

	rec->ir_free |= xfs_inobt_maskn(skip_agino - rec->ir_startino, 1);
}

/*
 * Set *cursor to the next allocated inode after whatever it's set to now.
 * If there are no more inodes in this AG, cursor is set to NULLAGINO.
 */
STATIC int
xchk_iscan_find_next(
	struct xchk_iscan	*iscan,
	struct xfs_buf		*agi_bp,
	struct xfs_perag	*pag,
	xfs_inofree_t		*allocmaskp,
	xfs_agino_t		*cursor,
	uint8_t			*nr_inodesp)
{
	struct xfs_scrub	*sc = iscan->sc;
	struct xfs_inobt_rec_incore	rec;
	struct xfs_btree_cur	*cur;
	struct xfs_mount	*mp = sc->mp;
	struct xfs_trans	*tp = sc->tp;
	xfs_agnumber_t		agno = pag->pag_agno;
	xfs_agino_t		lastino = NULLAGINO;
	xfs_agino_t		first, last;
	xfs_agino_t		agino = *cursor;
	int			has_rec;
	int			error;

	/* If the cursor is beyond the end of this AG, move to the next one. */
	xfs_agino_range(mp, agno, &first, &last);
	if (agino > last) {
		*cursor = NULLAGINO;
		return 0;
	}

	/*
	 * Look up the inode chunk for the current cursor position.  If there
	 * is no chunk here, we want the next one.
	 */
	cur = xfs_inobt_init_cursor(pag, tp, agi_bp);
	error = xfs_inobt_lookup(cur, agino, XFS_LOOKUP_LE, &has_rec);
	if (!error && !has_rec)
		error = xfs_btree_increment(cur, 0, &has_rec);
	for (; !error; error = xfs_btree_increment(cur, 0, &has_rec)) {
		xfs_inofree_t	allocmask;

		/*
		 * If we've run out of inobt records in this AG, move the
		 * cursor on to the next AG and exit.  The caller can try
		 * again with the next AG.
		 */
		if (!has_rec) {
			*cursor = NULLAGINO;
			break;
		}

		error = xfs_inobt_get_rec(cur, &rec, &has_rec);
		if (error)
			break;
		if (!has_rec) {
			error = -EFSCORRUPTED;
			break;
		}

		/* Make sure that we always move forward. */
		if (lastino != NULLAGINO &&
		    XFS_IS_CORRUPT(mp, lastino >= rec.ir_startino)) {
			error = -EFSCORRUPTED;
			break;
		}
		lastino = rec.ir_startino + XFS_INODES_PER_CHUNK - 1;

		/*
		 * If this record only covers inodes that come before the
		 * cursor, advance to the next record.
		 */
		if (rec.ir_startino + XFS_INODES_PER_CHUNK <= agino)
			continue;

		if (iscan->skip_ino)
			xchk_iscan_mask_skipino(iscan, pag, &rec, lastino);

		/*
		 * If the incoming lookup put us in the middle of an inobt
		 * record, mark it and the previous inodes "free" so that the
		 * search for allocated inodes will start at the cursor.
		 * We don't care about ir_freecount here.
		 */
		if (agino >= rec.ir_startino)
			rec.ir_free |= xfs_inobt_maskn(0,
						agino + 1 - rec.ir_startino);

		/*
		 * If there are allocated inodes in this chunk, find them
		 * and update the scan cursor.
		 */
		allocmask = ~rec.ir_free;
		if (hweight64(allocmask) > 0) {
			int	next = xfs_lowbit64(allocmask);

			ASSERT(next >= 0);
			*cursor = rec.ir_startino + next;
			*allocmaskp = allocmask >> next;
			*nr_inodesp = XFS_INODES_PER_CHUNK - next;
			break;
		}
	}

	xfs_btree_del_cursor(cur, error);
	return error;
}

/*
 * Advance both the scan and the visited cursors.
 *
 * The inumber address space for a given filesystem is sparse, which means that
 * the scan cursor can jump a long ways in a single iter() call.  There are no
 * inodes in these sparse areas, so we must move the visited cursor forward at
 * the same time so that the scan user can receive live updates for inodes that
 * may get created once we release the AGI buffer.
 */
static inline void
xchk_iscan_move_cursor(
	struct xchk_iscan	*iscan,
	xfs_agnumber_t		agno,
	xfs_agino_t		agino)
{
	struct xfs_scrub	*sc = iscan->sc;
	struct xfs_mount	*mp = sc->mp;
	xfs_ino_t		cursor, visited;

	BUILD_BUG_ON(XFS_MAXINUMBER == NULLFSINO);

	/*
	 * Special-case ino == 0 here so that we never set visited_ino to
	 * NULLFSINO when wrapping around EOFS, for that will let through all
	 * live updates.
	 */
	cursor = XFS_AGINO_TO_INO(mp, agno, agino);
	if (cursor == 0)
		visited = XFS_MAXINUMBER;
	else
		visited = cursor - 1;

	mutex_lock(&iscan->lock);
	iscan->cursor_ino = cursor;
	iscan->__visited_ino = visited;
	trace_xchk_iscan_move_cursor(iscan);
	mutex_unlock(&iscan->lock);
}

/*
 * Prepare to return agno/agino to the iscan caller by moving the lastino
 * cursor to the previous inode.  Do this while we still hold the AGI so that
 * no other threads can create or delete inodes in this AG.
 */
static inline void
xchk_iscan_finish(
	struct xchk_iscan	*iscan)
{
	mutex_lock(&iscan->lock);
	iscan->cursor_ino = NULLFSINO;

	/* All live updates will be applied from now on */
	iscan->__visited_ino = NULLFSINO;

	mutex_unlock(&iscan->lock);
}

/* Mark an inode scan finished before we actually scan anything. */
void
xchk_iscan_finish_early(
	struct xchk_iscan	*iscan)
{
	ASSERT(iscan->cursor_ino == iscan->scan_start_ino);
	ASSERT(iscan->__visited_ino == iscan->scan_start_ino);

	xchk_iscan_finish(iscan);
}

/*
 * Grab the AGI to advance the inode scan.  Returns 0 if *agi_bpp is now set,
 * -ECANCELED if the live scan aborted, -EBUSY if the AGI could not be grabbed,
 * or the usual negative errno.
 */
STATIC int
xchk_iscan_read_agi(
	struct xchk_iscan	*iscan,
	struct xfs_perag	*pag,
	struct xfs_buf		**agi_bpp)
{
	struct xfs_scrub	*sc = iscan->sc;
	unsigned long		relax;
	int			ret;

	if (!xchk_iscan_agi_needs_trylock(iscan))
		return xfs_ialloc_read_agi(pag, sc->tp, 0, agi_bpp);

	relax = msecs_to_jiffies(iscan->iget_retry_delay);
	do {
		ret = xfs_ialloc_read_agi(pag,